Producing rolled shapes of manganese steel.



UNITED STATES PATENT OFFICE.

WINFIELD S. POTTER, NEW YORK, N. Y.

PRODUCING ROLLED SHAPES OF MANGANESE STEEL.

No 'Drawing.

Specification of Letters Patent.

To all whom it may concern."

Be it known that I, WINFIELD S. Po'r'rnn, a citizen of the UnitedStates, residing in the city, county, and State of New York, haveinvented certain new and useful Improvements in Producing Rolled Shapesof Manganese Steel; and I do hereby declare the following to be a full,clear, and exact description of the invention, such as will enableothers skilled in the art to which it appertains to make and use thesame.

The object of my invention is to obtain reliably a rolled manganesesteel rail or bar with a continuous fine grained austenite structurethroughout; that is to say with the separable constituents of the metalin solution, and also with a continuous structure free fromirregularities or lamination.

A suitable method for obtaining the finished rail or bar in thedesirable finegrained condition is set forth in my application forLetters Patent of the United States, Ser. No. 604,996, filed January27th,

1911, for improvements in the heat treatment and rolling of manganesesteel.

I have found, in practice, that, in some instances because of thecharacter of the mill or particular conditions and exigencies at apartial separating out of the constituents which had been in solutionthroughout the metal, this separating out being particularly prominentin the thinner sections of the rail or bar. The rail or bar, in suchcases, correspondingly loses the uniformity of condition which it hasbeen the purpose of the treatment to attain, and if quenched or'otherwise rapidly cooled in its altered condition will have theseirregularities retained or made permanent in the completed product.

One' of the purposes of my present invention is to restore to thecondition suitable for quenching or rapid cooling a rail or bar whichafter leavingthe finishing pass of the rolls, has suffered in some ofits parts the separation referred to, so that thus restored andthereupon quenched or rapidly cooled, it will, as a final product, havethe same continuous fine grained austenite structure free fromirregularities or lammations and with its separable constituents insolution throughout substantially the same as if it had been immediatelyquenched or rapidly cooled upon its issuance from the finishing passesof the mill.

The method herein described further contemplates the avoidance oflamination in the rolled product by so conducting the manufacture thatthe ingot or bloom is prepared for' rolling without a formation of.

very large grainshaving smooth surfaces and feeble cohesion, such feeblecohering grains if present being elongated during rolling into fibers orsheets, which also have but feeble cohesion one with the other.

- In the practice of the invention, the steel, containing the desiredhigh proportion of manganese, carbon'and other elements, as for example,containing 13% of manganese, 1.25% of carbon, is so cast as to ob tain asound ingot free from pipes. This may be effected, for example, by usingmolds whose top section is of refractory material, or of chills thinnerthan the chills employed in the lower parts of the mold; so that themetal remains molten longest in the upper portion of the ingot. So also,the steel is preferably cast at a temperature notmuch above the freezingpoint of the metal so" of August 16, 1910, is also preferred so as torender the temperaturesv in the ingot higher and more uniform at thetime suitable for stripping than would be the case if the ordinary heavyiron mold were used.

When the ingot is frozen and has suitably cooled, depending upon thecharacter of the mold employed, the ingot is stripped andis placed in afurnace which, at the time, has a temperature not far removed from thesurface temperature of the ingot, and more especially is caution to beobserved in this partlcular if the ingot shall have retained any of itsfreezing structures when stripped. The ingot is then brought to atemperature of about 1200 C. and heated until in a plastic and uniformcon Patented Feb. 20,1912. Application filed October 30, 1911. SerialNo. 657,397.

- maximum without any long rest in its progress particularly any longrest above 1125 C. When the maximum temperature is reached this maximumtemperature is continued for such time only as to bring the mass to auniform temperature without detaining the ingot in the furnace beyondthis point, as by so doin coarse, feebly cohering grains would be ormedin the ingot.

The rail or other bar to be rolled may be obtained direct from the ingotin a continuous operation, or by rolling in stages after reheating thebloom; according to the arrangement of the mill or the particularsection of the rail or bar required. If conducted in stages, requiringthe reheating of the bloom, the bloom is preferably taken quickly fromthe blooming mill to the reheating furnace while still retaining as muchas possible of the initial heat in order to facilitate the reheatingoperation. The temperature of the reheating furnace at this time shouldclosely approximate the intended temperature to which the reheated bloomis to be brought, so that the reheat may be of short duration, such asto avoid excessive crystal building in the bloom;

It may be here noted that-an ingot which is finely recrystallized in themold by redistribution of the heat'of casting and which is thenintroduced with a high and nearly even temperature throughout into thesoaking pit may be brought rapidly to a temperature and conditionsuitable for rolling in a short time and without the progressivebuilding up of coarse, feebly coherent crystalline structures; and thatsimilarly, the bloom which is placed in the reheating furnacewith a highand nearly even temperature may be brought to a temperature andcondition suitable for further rolling with the smallest degree ofcrystal building and in thestate of substantial uniformity andcontinuity of. structure, whereby the characteristic lamination ofmanganese steel rolled from a blank, which has been either too slowlyheated or which has been over-heated may thus be avoided.

The temperature for the reheated bloom will depend largely upon thecharacter and extent of the work to which it is to be subjected in thefinishing passes of the mill, and may range from as low as 1000 G. inthose instances where the bar is to receive but one or two additionalpasses and is then to be immediately quenched, up to say 1225 C. incasethe percentage of reduction to the finished sectionis stillconsiderable and the shape to be produced is of such design that thegreatest plasticity of the bloom is requisite.-

To obtain in the finished bar a state of maximum strength and toughness,the finishing temperature, as the bar leaves the finishing pass of themill should be as uniform as posslble and as near 950 C. as possible,provided that the bar is thereupon immediately quenched. At all events,the parts of the bar that are to be subjected in use to Wear, as, forexample, the head portions of a rail should be rolled and quenched whilethe temperature is below 1075 C. or thereabout to. secure a fine graineddense steel, and these parts, as for example, the hotter head-portion ofa rail should be speedily cooled to about 1000 C. thereby so'equalizingthe temperatures as to avoid changes in the wrought state due to slowair cooling from higher temperatures; and the bar may be quickly brought'to the water and quenched, in accordance with my application forLetters Patent of the United States, Ser. No. 604996, while still in afine grained stiff and uniform condition. If the arrangements in themill, or the character of the section is such that the rail or bar cannot be reliably brought to the water while still having its separableconstituents in solution and while still retaining throughout thedesirable uniformity of temperature and condition, the finished barshould be taken as speedily as possible and with the least possible lossof temperature and change in condition to a reheating furnace (of thecontinuous type, for example) and therein equalized at about 1000 0.throughout and then quickly removed and quickly quenched.

The temperature at which the re-solution of the carbids of iron andmanganese can be quickly eflected ranges from about 975 C. upward. Thehigher the temperature of the reheating furnace, the shorter is the timerequired to bring the steel to temperatures above 975 (1, when thecarbids will be quickly taken into solution. I have found that thehigher the temperature to which the steel 1s brought the more rapidly isit recrystallized, and the size of the grain registers the highesttemperature at which any portion of the mass is permitted to rest evenfor so short a time, for examp e, as 10 mmutes; and thisrecrystallizing, if permitted, may even destroy entirely the finewrought state of the bar previously obtained during the rollingoperation. It is therefore very important that the finished bar shallnot be reheated throughout and allowed to rest in the reheating furnacelong at any high temperature, and particularly at temperatures above1075 C. or thereabout, above which point the bar if brought to an equalheat and allowed to rest soon assumes throughout a coarse grainedexcessively ductile and a than as above described, the time of subweakand unreliable condition. jecting them to the action of the equalizingThe reheating or equalizing furnace may furnace may be correspondinglyshortenedbe of the usual type, that is to say,-a furnace or lengthened,as the case may be and as may having a hearth on which the bars are tobebe necessary to restore the coldest parts to 70 placed and having areverberatory roof and the desirable uniform condition; whereupon aheating medium or flame below the roof, the bars will beremoved from theequalizing so that the bar is heated by radiation from furnace andquenched or rapidly, cooled to the flame and from the roof. Thereheating below 420 C. q

10 of the finished bar will be best conducted sub Having thus describedmy invention what 75 stantially as follows: The bar to be reheated Iclaim is p (being for example, a T-rail or a girder 1. The method ofproducing rolled shapes rail), having still from the heat of rolling, ofmanganese steel, which consists in first a temperature in its thickerhead portion heating a manganese steel ingot or bloom suflicient toretain in solution the separable until it is in a condition ofsubstantial. uni- 30 constituents of the steel, and having so farformity of distribution of its constituents, cooled in its base as to bein an unsuitable rolling'to finished shape with finishing temstate forquenching, will be placed on the peratures below 1075 (3., transferringto anhearth of the equalizing furnace head downequalizing furnace andsubjecting it to an ward, or on its side with the head inclinedequalizing reheat therein at such temperag downward, so as to expose thecooler parts ture as will effect the re-solution of any carof the railto the radiation from above. The bids that may have se arated and untilsuch flame and roof temperature of the furnace is resolution has been eected, terminating. the maintained preferably at about 1025 C. soequalizing reheat before any substantial loss that the bar may remain inthe furnace for of-the wrought condition has occurred, and a few minutesafter its temperatures have then quenching; substantially as described,become equalized without considerable alter- 2. The method of-producingrails of manation of structure other than the desiredreganese steel,which consists in first heating solution of carbids and for such time aswill a manganese steel ingot or bloom until it is 30 surely effect suchsolution. The bar, leavin a condition-of substantial uniformity-of ingthe mill at say 1025 C. in its hottest distribution. of itsconstituents, rolling to portions and at say 950 C. in its coolestporfinished shape with finishing temperatures tions will move to thefurnace in say 30 seebelow 1075 C. in the parts of the rail that ondswith a loss of about 50 C. in its averare to be subjected in use towear, transfer- 35 age temperature. Its coldest parts may then ring toan equalizing furnace and subjecthave a temperature below 900 C. andthese ing the rail therein to an equalizing reheat coldest partswillhave begun to suffer a sepat such temperatures as will effect theresoaration of carbids and a transition from a lution of any carbidsthat may have sepa uniform austenite structure. The bar being rated anduntil such re-solution has been 40 placed in the equalizing furnacewithout effected, terminating the equalizing reheat further loss of timeis brought back to say before any substantial loss of the wrought 1000C. in about 5 minutes and may then be condition has occurred and thenquenching; quenched at once, or it may be detained in substantially asdescribed. the furnace for say 5 additional minutes to 3, The m thod ofroducing rails of man- 45 ore nearly equalize its temperatures beganesesteel, which consists in first heating fore quenching. After obtainingan equal an ingot above 1125 C. until in a uniform temperature above 975C. or thereabout no coh r nt ondition, rolling to a bloom, readditionalstay in the furnace is necessary heating the bloom and equalizing for ashort or advisable, inasmuch as immediately after time at temperaturesbetween 1000 C. and

50 solution of the carbids is complete, grain 1225 C., rolling to a railwith a finished building would begin with a rapid loss of temperaturebelow 1075 C.,equal1z1ng for a stiffness, hardness and strength of thesteel. short time, and quenching; substantlally as In fact, theseobjectionable changes proceed described. H so rapidly at 1100 (1, forexample, that as 4. The method 61 producing rails of man- 55 short adelay as one minute after the bar ,ganeses trfl, which consists in firstheating has been equalized at this p irglsrefiough an ingot above 11250., until in a uniform to cause a c n i ljlibleq -osspf quality. Thecoherent condition, rolling to a rail with a bar sliguld there fore, bekept in the furnace finishing temperature below 107 5 (3., equal-.-l1nder a rapidly rising heat until its temperizing for a short time,and quenching; suboo atures are nearly or quite equalized abovestantially as described. 975 C. throughout the bar, and the car- 5. Themethod of producing rails of manbids will then be insolution whereuponthe ganese steel, which consists in first heating bar should beimmediately removed and an ingot above 1125 C. until in a uniform vquenched. In those instances when the bars coherent condition, rollingto a rail wlth a 65 reach the equalizing furnace hotter or colderfinishing temperature of about 950 0.,

equalizing for a short time at about 975 C. about 1000 (3., and shortlythereafter 10 to 1025 C., and quenching; substantially as quenching;substantially as described.

' described. In testimony whereof I afiix my signature,

ganese steel, which consists in first heating 6. The method of producingrails of manin presence of two witnesses.

an ingot above 1125 (1., until in a uniform WINFIELD POTTER coherentcondition, rolling to a rail with a YVitnesses:

finishing temperature below 107 5 0., equal- JOHN C. PENNIE, izing thetemperatures of the finished rail at M. A. BILL.

